Is it real?
A mashup clip and a mashup you can launch are different things. The directory uses three labels so you do not have to guess.
Playable download
The creator published a build, or a launcher page that installs one, and wrote down the games and versions. SkyCraft, ER Mario, and the MW2 mashup are in this group. You still need the games they name. We do not host the files.
DIY build
There is source, and no one-click release. The Mac Elden Ring bridge and ArkWeb are like this. A GitHub page is real. It is not the same as a zip you can double-click.
Video only
Someone posted footage, and the coverage we checked did not include a repo or a release. The Minecraft in Elden Ring clip is the famous case. A later project can exist under another name. The pair page says so when we have found one.
What to open first
Use the play finder if you already own the games. Read how to spot a fake download before you run a file from a reply, a repost, or a page that is not the creator's.